[PATCH v4 1/4] arm64/mm: generalize PMD_PRESENT_INVALID for all levels

[Ryan Roberts <ryan.roberts@arm.com>]

As preparation for the next patch, which frees up the PTE_PROT_NONE
present pte and swap pte bit, generalize PMD_PRESENT_INVALID to
PTE_PRESENT_INVALID. This will then be used to mark PROT_NONE ptes (and
entries at any other level) in the next patch.

While we're at it, fix up the swap pte format comment to include
PTE_PRESENT_INVALID. This is not new, it just wasn't previously
documented.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---
 arch/arm64/include/asm/pgtable-prot.h |  8 ++++----
 arch/arm64/include/asm/pgtable.h      | 21 ++++++++++++---------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index dd9ee67d1d87..cdbf51eef7a6 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -21,11 +21,11 @@
 #define PTE_PROT_NONE		(_AT(pteval_t, 1) << 58) /* only when !PTE_VALID */
 
 /*
- * This bit indicates that the entry is present i.e. pmd_page()
- * still points to a valid huge page in memory even if the pmd
- * has been invalidated.
+ * PTE_PRESENT_INVALID=1 & PTE_VALID=0 indicates that the pte's fields should be
+ * interpreted according to the HW layout by SW but any attempted HW access to
+ * the address will result in a fault. pte_present() returns true.
  */
-#define PMD_PRESENT_INVALID	(_AT(pteval_t, 1) << 59) /* only when !PMD_SECT_VALID */
+#define PTE_PRESENT_INVALID	(_AT(pteval_t, 1) << 59) /* only when !PTE_VALID */
 
 #define _PROT_DEFAULT		(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
 #define _PROT_SECT_DEFAULT	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index afdd56d26ad7..7156c940ac4f 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -132,6 +132,8 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
 #define pte_dirty(pte)		(pte_sw_dirty(pte) || pte_hw_dirty(pte))
 
 #define pte_valid(pte)		(!!(pte_val(pte) & PTE_VALID))
+#define pte_present_invalid(pte) \
+	((pte_val(pte) & (PTE_VALID | PTE_PRESENT_INVALID)) == PTE_PRESENT_INVALID)
 /*
  * Execute-only user mappings do not have the PTE_USER bit set. All valid
  * kernel mappings have the PTE_UXN bit set.
@@ -261,6 +263,13 @@ static inline pte_t pte_mkpresent(pte_t pte)
 	return set_pte_bit(pte, __pgprot(PTE_VALID));
 }
 
+static inline pte_t pte_mkinvalid(pte_t pte)
+{
+	pte = set_pte_bit(pte, __pgprot(PTE_PRESENT_INVALID));
+	pte = clear_pte_bit(pte, __pgprot(PTE_VALID));
+	return pte;
+}
+
 static inline pmd_t pmd_mkcont(pmd_t pmd)
 {
 	return __pmd(pmd_val(pmd) | PMD_SECT_CONT);
@@ -478,7 +487,7 @@ static inline int pmd_protnone(pmd_t pmd)
 }
 #endif
 
-#define pmd_present_invalid(pmd)     (!!(pmd_val(pmd) & PMD_PRESENT_INVALID))
+#define pmd_present_invalid(pmd)	pte_present_invalid(pmd_pte(pmd))
 
 static inline int pmd_present(pmd_t pmd)
 {
@@ -508,14 +517,7 @@ static inline int pmd_trans_huge(pmd_t pmd)
 #define pmd_mkclean(pmd)	pte_pmd(pte_mkclean(pmd_pte(pmd)))
 #define pmd_mkdirty(pmd)	pte_pmd(pte_mkdirty(pmd_pte(pmd)))
 #define pmd_mkyoung(pmd)	pte_pmd(pte_mkyoung(pmd_pte(pmd)))
-
-static inline pmd_t pmd_mkinvalid(pmd_t pmd)
-{
-	pmd = set_pmd_bit(pmd, __pgprot(PMD_PRESENT_INVALID));
-	pmd = clear_pmd_bit(pmd, __pgprot(PMD_SECT_VALID));
-
-	return pmd;
-}
+#define pmd_mkinvalid(pmd)	pte_pmd(pte_mkinvalid(pmd_pte(pmd)))
 
 #define pmd_thp_or_huge(pmd)	(pmd_huge(pmd) || pmd_trans_huge(pmd))
 
@@ -1251,6 +1253,7 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
  *	bits 3-7:	swap type
  *	bits 8-57:	swap offset
  *	bit  58:	PTE_PROT_NONE (must be zero)
+ *	bit  59:	PTE_PRESENT_INVALID (must be zero)
  */
 #define __SWP_TYPE_SHIFT	3
 #define __SWP_TYPE_BITS		5
-- 
2.43.0